TY - JOUR A1 - Ivanov, Valentin D. A1 - Cioni, Maria-Rosa L. A1 - Bekki, Kenji A1 - de Grijs, Richard A1 - Emerson, Jim A1 - Gibson, Brad K. A1 - Kamath, Devika A1 - van Loon, Jacco Th. A1 - Piatti, Andres E. A1 - For, Bi-Qing T1 - New quasars behind the Magellanic Clouds. Spectroscopic confirmation of near-infrared selected candidates JF - Current biology N2 - Context. Quasi-stellar objects (quasars) located behind nearby galaxies provide an excellent absolute reference system for astrometric studies, but they are difficult to identify because of fore-and background contamination. Deep wide-field, high angular resolution surveys spanning the entire area of nearby galaxies are needed to obtain a complete census of such quasars. Aims. We embarked on a program to expand the quasar reference system behind the Large and the Small Magellanic Clouds, the Magellanic Bridge, and the Magellanic Stream that connects the Clouds with the Milky Way. Methods. Hundreds of quasar candidates were selected based on their near-infrared colors and variability properties from the ongoing public ESO VISTA Magellanic Clouds survey. A subset of 49 objects was followed up with optical spectroscopy. Results. We confirmed the quasar nature of 37 objects (34 new identifications): four are low redshift objects, three are probably stars, and the remaining three lack prominent spectral features for a secure classification. The bona fide quasars, identified from their broad emisison lines, are located as follows: 10 behind the LMC, 13 behind the SMC, and 14 behind the Bridge. The quasars span a redshift range from z similar to 0.5 to z similar to 4.1. Conclusions. Upon completion the VMC survey is expected to yield a total of similar to 1500 quasars with Y < 19.32 mag, J < 19.09 mag, and K-s < 18.04 mag. KW - surveys KW - infrared: galaxies KW - quasars: general KW - Magellanic Clouds Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201527398 SN - 1432-0746 VL - 588 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Oskinova, Lida A1 - Bulik, Tomasz A1 - Gomez-Moran, Ada Nebot T1 - Infrared outbursts as potential tracers of common-envelope events in high-mass X-ray binary formation JF - Astronomy and astrophysics : an international weekly journal N2 - Context. Classic massive binary evolutionary scenarios predict that a transitional common-envelope (CE) phase could be preceded as well as succeeded by the evolutionary stage when a binary consists of a compact object and a massive star, that is, a high-mass X-ray binary (HMXB). The observational manifestations of common envelope are poorly constrained. We speculate that its ejection might be observed in some cases as a transient event at mid-infrared (IR) wavelengths. Aims. We estimate the expected numbers of CE ejection events and HMXBs per star formation unit rate, and compare these theoretical estimates with observations. Methods. We compiled a list of 85 mid-IR transients of uncertain nature detected by the Spitzer Infrared Intensive Transients Survey and searched for their associations with X-ray, optical, and UV sources. Results. Confirming our theoretical estimates, we find that only one potential HMXB may be plausibly associated with an IR-transient and tentatively propose that X-ray source NGC4490-X40 could be a precursor to the SPIRITS 16az event. Among other interesting sources, we suggest that the supernova remnant candidate [BWL2012] 063 might be associated with SPIRITS 16ajc. We also find that two SPIRITS events are likely associated with novae, and seven have potential optical counterparts. Conclusions. The massive binary evolutionary scenarios that involve CE events do not contradict currently available observations of IR transients and HMXBs in star-forming galaxies. KW - X-rays: binaries KW - stars: massive KW - infrared: general KW - infrared: galaxies Y1 - 2018 U6 - https://doi.org/10.1051/0004-6361/201832925 SN - 0004-6361 SN - 1432-0746 VL - 613 PB - EDP Sciences CY - Les Ulis ER -